In applications such as broadcast, cable and satellite television and radio, tuning and demodulation functions are typically performed by one or more integrated circuits. The tuner is often an analog/RF module or integrated circuit supplying an analog signal to the demodulator. The demodulator has a data converter and often has a dedicated digital circuit which processes the converted signal and generates a data transport stream. The data stream typically contains the compressed video stream in, for example, the MPEG2 format when the DVB-T standard is used.
FIG. 1 is a block diagram of an analog tuner 10 in communication with a demodulator 30, as known in the prior art. Tuner 10 is shown as including a low-noise amplifier (LNA) 12, a mixer 14 adapted to receive a clock signal generated by local oscillator (LO) 16, an intermediate frequency (IF) filter 18 and a variable gain block 20. Demodulator 30 is shown as including an analog-to-digital converter (ADC) 32, a digital baseband modulator/demodulator (MODEM) 34 and a digital interface 36. Digital interface 36 may be a USB2.0 or PCI Express that supplies a transport stream to host CPU 40. MODEL 34 performs modulation and demodulation operations.
FIG. 2 is a block diagram of an analog RF tuner and demodulator 50, also known in the prior art. The system shown in FIG. 2 is similar to that shown in FIG. 1 except that in the system shown in FIG. 2, analog tuner 10 and demodulator 30 are disposed in the same integrated circuit or module 50. For the systems shown in both FIGS. 1 and 2, host CPU 40 is adapted to receive the transport date stream from the digital interface and process typical software applications. In conventional systems, host CPU 40 is not adapted to perform any demodulation operations.